Hot water heater



May 17, 1966 A. MERINO HOT WATER HEATER Filed March 27, 1961 I N V EN TOR.

ATTORNEYS.

United States Patent 3,251,346 HOT WATER HEATER Alfonso Merino, South Gate, Calif., assignor to Rheem Manufacturing Company, Chicago, 11]., a corporation of California Filed Mar. 27, 1961, Ser. No. 98,649 2 Claims. (Cl. 122-17) This invention relates to hot water heaters and more particularly to a tank type underfired heater.

One of the problems encountered with underfired Water heaters is excessive temperature buildup in the water in the upper part of the tank which normally results from repetitive withdrawals of small volumes of hot water.

In anormal water heater of this type, the water tem-- perature is controlled by a thermostat located near the bottom of the tank. The cold Water is introduced into the'tank near the bottom as hot water is drawn oft" at the top. The thermostat quickly senses the cold Water and reacts to introduce heat to the tank. This raises the temperature of the cold water just introduced but there is also a heat transfer that takes place, through the flue ways discharging the hot flue gases, into the water at the top of the tank.

Since this entire operation takes. place after all the Water in the tank has reached some desired maximum temperature, say around 150 F. for normal domestic use or 180 F. for commercial use-and since the cold water introduced at the bottom of the tank normally stays at the bottom because of its higher specific gravitythe heat transfer from the flue gases to the water in the top of the tank will increase that water temperature somewhat and the thermostat being in the bottom of the tank will not sense this temperature increase. As a result, on short repetitive draws of hot water, the water temperature in the top of the tnak may gradually build up to a dangerous level.

One way of controlling lhiS'filTBCt is by placing a second thermostat at the top of the tank which Will override the bottom thermostat and not permit the burners to operae when the water temperature at the top of the tank is above normal. This is not only expensive but it reduces The above and other objects and features of the invention will be more readily apparent from the accompanying description-when read in connection with the accompanying drawing, in which:

FIGURE 1 is a sectional view thorugh a hot water heater embodying the invention; and

FIGURES 2 and 3 are partial sectional views illustrating alternative control devices.

The hot Water heater, as shown in FIGURE 1, is of a conventional underfired tank type including a vertically elongated tank 10 having an upwardly domed bottom 11 and provided with a hot water outlet 12 opening into its top. The cold water supply conduit 13 extends vertically through the top of the tank and opens near the bottom of the tank for'supply of cold water thereto.-

The Water in the tank is heated by a fuel burner, 14,

such as a conventional gas burner, mounted below the domed bottom 11. The products of combustionfrom the burner are discharged through a flue 15 extending ver tically through the tank and connected to a suitable stack or the like above the top of the tank. The burner is con- I trolled by a thermostat 16 extending into the lower part of the tank in the usual manner so that the burner will be turned on when the thermostat senses a temperature below the desired value and will be turned off when the thermostat senses a temperature at 'or above the desired value.

According to the present invention, the Water supply the amount of hot water available from the water heater by delaying the heating ofthe cold water introduced at the bottom.

Another method of overcoming this eifect is by introducing the cold water higher up in the tank so that it dilutes the temperature in the upper part of the tank. This is the method usually employed, but it results in reduction of the amount of stored hot Water available from the tank. The normal design in this regard will permit the withdrawal of only 60% of the hot water capacity of the tank with a temperature drop of 30 F. from the start of the draw to the end.

It is one of the objects of the present invention to provide a hot water heater in which excessive heating of the water in the upper part of the tank is eliminated without reducing the amount of stored hot water available from the tank.

According to a feature of the invention, cold water is discharged into the upper part of the tank from the cold water supply conduit under the control of a thermostat responsive to the temperature in the upper part of the tank. In this way, only the amount of cold water required to prevent excessive temperature buildup is discharged into the upper part of the tank so that the effective capacity of the tank is not reduced. It has been found, in fact, that with the present invention excessive temperature buildup in the upper part of the tank can be prevented while providing as much as 90% of the normal hot water capacity of the tank.

water discharge openings 21 opening from the supply conduit into the upper part of the tank. Discharge of water through the openings 21 is controlled thermostatically by a bimetal strip 22 secured at one end to the exterior of the conduit as by means of a rivet 23 with its free end bent over, as indicated at 24, to move transversely into the conduit through an opening 25 downstream from the openings 21. In this construction when the end portion 24 of the thermostat is moved into the conduit it tends to create a restriction therein increasing the flow of water through the discharge openings 21 to increase, the discharge of cold water into the upper part of the tank. When the water in the upper part of the tank is at or below the desired maximum temperature, the thermostat 22 will deflect to remove the bent over end 24 thereof from the conduit so that incoming water can flow through the conduit to the lower end thereof without obstruction. At this time, very little water will discharge through the openings 21 so that over dilution of the hot water in the upper portion of the tank will not occur In operation of the unit, when the water in the tank is at the desired temperature substantially throughout the full height of the tank, the thermostat 22 will deflect to move the end 24 thereof out of the conduit so that a minimum amount of wtaer will flow through openings 21. As water is withdrawn from the tank and fresh cold water is introduced through the supply conduit, the thermostat 16 will sense a temperature below the desired temperature and will turn the burner on. The burner not only will heat the water in the tank through the tank bottom but Will also heat the water in the upper portion of the tank due to passage of combustion products through the flue 15. Due to this effect and to the natural tendency of the water in the tank to stratify, the water in the upper part of the tank will-tend to achieve a temperature higher than the desired maximum value. When this occurs the thermostat 22 will deflect to move the end 24 into the conduit so that when water is introduced to the tank a greater portion of the incoming cold water will flow through the openings 21 into the upper part of the tank. Dilution of the excessively hot water in the upper part of the tank will reduce its temperature to the desired maximum value at which time the thermostat will again move the end 24 out of the conduit so that overcooling cannot occur. In this way, the temperature of the water in the upper part of the tank is automatically maintained at the desired maximum temperature without excessive overcooling, which would reduce the efiective capacity of the tank.

The embodiment shown in FIGURE 3 is like that of FIGURE 2 in that the supply conduit 13 is formed with one or more water discharge openings 31 and a vane element 32 is moved into the conduit downstream from the discharge openings variably to obstruct flow through the conduit. In this case, the vane 32 is moved into and out of the conduit by a bellows 33 mounted in a housing 34 on the exterior of the conduit and connected to a bulb 35 supported in the upper part of the tank. The bulb and bellows are connected in a closed system and are filled with an expansible fluid so that upon an increase in temperature of the water in the upper part of the tank the bellow will be caused to expand and move the vane 32 into the conduit thereby to increase the discharge of water through the openings 31. As the water temperature is reduced to the desired maximum value, the fluid in the bulb and bellows will contract to withdraw the vane 32 from the conduit so that the water can flow therethrough with a minimum of obstruction and with a minimum of discharge through the openings 31.

While several embodiments of the invention have been shown and described herein, it will be understood that they are illustrative only and not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. A hot water heater comprising a vertically elongated tank to contain water, heating means to heat the water in the tank, thermostatic means responsive to the temperature in the lower part of the tank controlling the heating means, a water outlet connection at the top of the tank, a water supply conduit extending vertically downward into the tank and opening in the lower portion of the tank, said supply conduit having awater discharge opening therein in the upper part ofthe tank, and thermostatic means in the upper part of the tank controlling the rate of water discharge through this water discharge opening, said thermostatic means comprising a vane element movable into the supply conduit downstream from the water discharge opening variably to obstruct the conduit.

2. A hot water heater comprising a vertically elongated tank to contain hot water, a water outlet connection at the top of the tank, a water supply conduit extending vertically downward into the tank and opening in the lower portion thereof, a fuel burner below the bottom of the tank, a flue extending upward through the tank through which hot combustion products from the burner pass, thermostatic control means for the burner respon-, sive to the temperature in the lower part of the tank, the supply conduit having a discharge opening therein in the upper part of the tank, and thermostatic means in the upper part of the tank controlling the rate of water discharge through the discharge opening, said last named thermostatic means comprising a vane member movable into the supply conduit downstream from the discharge opening variable to restrict the conduit.

References Cited by the Examiner UNITED STATES PATENTS 1,681,377 8/1928 Stack. 2,115,601 4/1938 Whitby et'al. 2,504,092 4/1950 Thomas 122-17 2,592,863 4/ 1952 Conner 126-362 X 2,814,279 11/1957 Thomas 126362 X FOREIGN PATENTS 282,075 8/ 1928 Great Britain.

FREDERICK L. MATTESON, 111., Primary Examiner. PERCY L. PATRICK, ROBERT A. DUA, Examiners. 

1. A HOT WATER HEATER COMPRISING A VERTICALLY ELONGATED TANK TO CONTAIN WATER, HEATING MEANS TO HEAT THE WATER IN THE TANK, THERMOSTATIC MEANS RESPONSIVE TO THE TEMPERATURE IN THE LOWER PART OF THE TANK CONTROLLING THE HEATING MEANS, A WATER OUTLET CONNECTION AT THE TOP OF THE TANK, A WATER SUPPLY CONDUIT EXTENDING VERTICALLY DOWNWARD INTO THE TANK AND OPENING IN THE LOWER PORTION OF THE TANK, SAID SUPPLY CONDUIT HAVING A WATER DISCHARGE OPENING THEREIN IN THE UPPER PART OF THE TANK, AND THERMOSTATIC MEANS IN THE UPPER PART OF THE TANK CONTROLLING THE RATE OF WATER DISCHARGE THROUGH THIS WATER DISCHARGE OPENING, SAID THERMOSTATIC MEANS COMPRISING A VANE ELEMENT MOVABLE INTO THE SUPPLY CONDUIT DOWNSTREAM FROM THE WATER DISCHARGE OPENING VARIABLY TO OBSTRUCT THE CONDUIT. 